Testimonial to Stan Kaplan

by B. John Garrick

His work in nuclear reactor space-time kinetics in the nuclear field, his computational methods for determining the size and location of tumors, and his analytical methods for quantifying the risk of complex systems established him as a thought leader in several fields. Stan's greatest asset was his passion for clarity of thought. He was not one to hide behind esoteric technical lingo. He was probably the clearest thinker with whom I had the pleasure of being associated. He was a "gap bridger" between science and engineering, theory and practice, while understanding both enough that with his superb mathematical skills was able to make the important connections for real world problem solving.

My relationship with Stan Kaplan began in 1954 when we were both students at a special graduate program in nuclear science and engineering sponsored by the United States Atomic Energy Commission (AEC) known as the Oak Ridge School of Reactor Technology (ORSORT). While Stan came to ORSORT as a graduate in civil engineering from the City College of New York, he was more of an applied mathematician than an engineer. Following his 12 months at ORSORT, he took a position with the Westinghouse Bettis Laboratories in Pittsburgh in reactor physics to develop analytical methods for designing nuclear propulsion systems for the U.S. Navy. I went in a different direction, first to Washington, D.C., to work as a nuclear reactor analyst for the AEC for a couple of years prior to heading out west to start up a nuclear science and engineering capability in a west coast engineering firm. Both of us continued our graduate programs while retaining our professional affiliations and received PhDs—Stan in mechanical engineering and applied math from the University of Pittsburgh. My degree was in engineering and applied science from the University of California, Los Angeles. Meanwhile, because of the bond we created at ORSORT, we stayed in close contact and always had the vision that sooner or later we would find a way to work together on something of mutual interest.

It was while I was doing my PhD thesis at UCLA that we found a topic of high mutual interest. Stan became very interested in the topic of my thesis, probabilistic risk assessment, an interest that received an enormous boost by our mutually attending a short course at UCLA given by Professor E. T. Jaynes, then of Stanford University and Myron Tribus then of UCLA. The course was on probability theory and information theory. It was terrific, very Bayesian, and fit superbly well with the thought processes to which both Stan and I had a great affinity. This short course, my thesis, and many important consulting assignments triggered several decades of collaboration on risk assessment methods and applications. Our goal was to evolve a general theory of quantitative risk assessment with only the boundary conditions and phenomenological considerations changing. Even though different types of expertise are involved for different applications, the idea was to develop a QRA thought process anchored to a few basic tenets. The triplet definition of risk, first noted in 1968 in my thesis but without the triplet name, is an example of such a tenet. It was much later, 1981 that we collaborated on the triplet interpretation of risk and formalized the definition in a joint paper published as paper number 1 in issue number 1 of Risk Analysis, an international journal. This was followed by many projects in which we developed or identified methods and approaches for processing data and evidence, structuring scenarios, assembling risk curves, and representing the uncertainties involved in a quantitative form. The emphasis was always on answering the question, what is the risk, for complex natural and engineered systems for the purpose of making good decisions on how to manage such systems. The tenets and concepts that worked best are mostly captured in the text of which I was the principal author, Quantifying and Controlling Catastrophic Risks, published by Elsevier (Academic Press) and dedicated to Stan Kaplan. But it is the behind the scene papers and studies leading up to the book that capture the essence of the evolving theory. In that regard, it is the desire to make some of the key references and papers from Stan and myself available that are relevant to this off and on half century of collaboration. Of course, many of the papers are on topics outside the risk field.

It is with regret that I acknowledge that the collaboration is no longer active as Stan passed away on June 6, 2011, from Alzheimer's, which makes exposing his work even more important. In that connection, included in this testimony is my introduction of Stan when he received the 1996 Distinguished Achievement Award from the Society for Risk Analysis, an international society. It should be noted that in addition to the many honors noted in the following introduction, Stan was later granted the highest honor an engineer can receive; he was elected to the National Academy of Engineering in 1999.